Sometimes when connecting to the PoliteMail Server, typically after an update to Outlook or PoliteMail, you login credentials may fail, despite being accurate.
This is typically due to an Internet Explorer cache issue. The solution is to clear your IE cache (as Outlook only utilizes IE, it doesn’t matter what browser you use, you must clear the IE cache).
Clearing your internet cache should always be one of your first troubleshooting steps when encountering an issue with PoliteMail.
If you are using IE9 or later (see below for Edge, IE8 or earlier)
1. Close Outlook and open Internet Explorer. Using CTRL+SHIFT+DELETE will open the clear cache window immediately.
or
Click the gear button at the top right (under the red close window button). 
2. Select the Safety menu option, then Delete browsing history.
3. In the Delete Browsing History dialog, select Temporary Internet Files, Cookies, and History.
5. Click the Delete button at the bottom.
6. Close IE and restart Outlook.
If you are using Microsoft Edge:
1. Close Outlook and open Internet Explorer. Using CTRL+SHIFT+DELETE will open the clear cache window immediately.
or
2. Click the 3 dots on the upper right-hand side of the screen.
3. Choose History > Clear Browsing Data.
4. Make sure the first four options are checked, and then choose Clear Now.
5. Close IE and restart Outlook.
If you are using Internet Explorer 8
If you are using IE8 or earlier, to get to the Delete Browsing History dialog, start from the IE menu, select Tools, then Delete Browsing History…
Close IE and restart Outlook.